Asphalt Rubber Technology Information Center
Residue By-Product From an Atmospheric Fluidized Bed Combustion Process Used in Highway
Subgrade Modification
Hopkins, Tommy; Hunsucker, David and Beckham, Tony, University of Kentucky  
October, 1993          
Key Words:

A spent lime residue from an atmospheric fluidized bed combustion process was used to modify two highway soil
subgrade sections on a route in Kentucky.  The AFBC residue contains high percentages of CaO, Ca(OH)2, and MgO and
produces soil-lime pozzolanic reactions when mixed with clayey soils to form cementing-type materials.  About two
months after stabilization, non-uniform heave occurred in the asphaltic base course surface.  Final surfacing was
delayed and field and laboratory studies were initiated.  Long-term swell test, lasting up to 186 days, were performed on
compacted specimens containing different percentages of the spent lime residue and subgrade soils.  Optical survey
points established on the pavement surfaces were monitored over a period of about 5.5 years.
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